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// This Source Code is in the Public Domain per: http://litesoft.org/License.txt package org.litesoft.core.util; import java.util.*; /** * There are two points for having this class:<p> * <p/> * First, that all Iterators need to be able to throw NoSuchElementException if * next is inappropriately called. The easiest way is to simply implement a * dumb next at a superclass level that always throws it.<p> * <p/> * Second, the SUN/Java Iterators should NOT have supported <i>remove()</i>. * The GOF (Gang Of Four) Iterator not only provided more funcationality * (supporting both multiple reads of the current item AND the ability to pass * over the collection multiple times), but provided a nice <i>read only</i> * view of an arbitrarily stored collection. To <i>restore</i> the read only * view aspect of an Iterator, this class provides a <i>final</i> implimentation * of <i>remove()</i>.<p> * * @author George Smith * @version 1.0 7/28/01 * @see <a href="http://java.sun.com/j2se/1.3/docs/api/java/lang/Util/Iterator.html">java.util.Iterator</a> */ public abstract class AbstractReadOnlyIterator<T> implements Iterator<T>, Disposable { /** * hasNext() is part of the Iterator interface. It is abtract here * because there is no reasonable, common, implementation and to * remind the developer who extends this class that they, at a * minimum, need to implement it.<p> * * @see <a href="http://java.sun.com/j2se/1.3/docs/api/java/lang/Util/Iterator.html#hasNext()">java.util.Iterator#hasNext()</a> */ @Override abstract public boolean hasNext(); /** * All most all Iterators will need to throw NoSuchElementException * at some point, so this is simply a convenience implementation.<p> * * @throws NoSuchElementException * @see <a href="http://java.sun.com/j2se/1.3/docs/api/java/lang/Util/Iterator.html#next()">java.util.Iterator#next()</a> */ @Override public T next() { throw new NoSuchElementException(); } /** * As mentioned above, the SUN/Java Iterators should NOT have supported * <i>remove()</i>.<p> * <p/> * Therefor, this method is a <i>final</i> version that throws * UnsupportedOperationException.<p> * * @throws UnsupportedOperationException * @see <a href="http://java.sun.com/j2se/1.3/docs/api/java/lang/Util/Iterator.html#remove()">java.util.Iterator.remove()</a> */ @Override public final void remove() { throw new UnsupportedOperationException(); } @Override public void dispose() { } } |